Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, openWorld, non-idempotent and non-destructive. The description adds genuinely useful undisclosed context – call cost/billing source and account-type restriction – but says nothing about failure behavior for unresolvable names or network-specific quirks.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Two tight sentences, the core behavior and example first, the cost and eligibility constraints second. No filler.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a two-param read tool with full schema coverage and no output schema, the description covers inputs, outputs (address or primary name), cost and platform limits. Only the error/empty-resolution case is left unstated.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so both parameters and their semantics are already documented. The description's mention of name-in/address-in mirrors the schema's own 'input' description, so it adds little beyond the structured fields; baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific bidirectional verb+resource: turns an ENS name into an address or an address into its primary ENS name, with a concrete example (vitalik.eth). Nothing among the siblings overlaps, so differentiation is implicit and adequate.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives clear context for use plus hard constraints: pay-per-call against SingIt limits in USDC and Base accounts only for now. It stops short of naming an alternative tool or a when-not condition, but no close sibling exists to route to.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.